Recently, cameras equipped with a camera shake correction function come into general use. With such a camera, even when a photographer performs image shooting by handheld, it allows the photographer to shoot images with no image blur without particularly paying attention to camera shaking.
In general, the correction capability of the camera shake correction function of a camera is indicated by the value of a shutter speed (exposure time) with which image blur can be corrected. This is represented by the ratio between a shutter speed at which the influence of image blur caused by camera shaking starts to be seen within an image that is shot without executing the camera shake correction function (this is also called a camera-shake limit shutter speed), and a shutter speed at which the influence of image blur caused by camera shaking starts to be seen within an image that is shot with the camera shake correction function executed.
In the meantime, a conventionally known mechanism for correcting camera shaking is, for example, the following. First, an image blur amount (image plane movement amount) based on a postural change in a camera body caused by camera shaking is detected by, for example, a gyro sensor that corresponds to a camera shake detection unit. Then, an image blur correction amount is calculated from the image blur amount detected by the camera shake detection unit. In addition, an image blur correction unit for making an image blur correction moves, on the basis of the calculated image blur correction amount, an optical system or an image sensor in a direction in which the image blur amount detected by the camera shake detection unit is cancelled. This suppresses image blur generated on an imaging plane.
The prior art includes the following camera shake correcting methods.
A method disclosed in patent document 1 (Japanese Laid-open Patent Publication No. 2011-145354) is provided with: an angular velocity sensor that detects camera shaking; a high-pass filter performing processing to attenuate a shake signal of a frequency lower than a first crossover frequency to the detected shake signal; a phase compensating filter compensating the phase shift of a signal which has been processed by the high-pass filter from the phase of a signal which has not been processed yet; and a blur correction unit correcting the shaking of the imaging apparatus based on the shake signal whose phase shift has been compensated by the phase compensating filter. The phase compensating filter changes the phase so as to cancel the phase shift caused by the high-pass filter, thereby preventing the phase shift from decreasing the correction capability.
According to a method disclosed in patent document 2 (Japanese Laid-open Patent Publication No. 2006-139095), an integrated value of an angular velocity is calculated by reading (sampling) the angular velocity outputs of a gyro sensor at a certain interval of time and subjecting them to time integration, and then an amount of change in integrated value is calculated from a difference between the thus calculated integrated value and the previous integrated value; based upon control time and a delay time determined by the amount of change and a blur correction module, an acceleration value is calculated in order to obtain an amount of movement of a shift lens, by which the inclination of the optical axis of the lens can be offset; subsequently, the thus calculated acceleration value is added to the integrated value calculated at this time, and then a control value for moving a shift lens is calculated using the integrated value after the addition. Driving the shift lens using the thus calculated control value obtains a blur-free photographic image.